Many chemical reactions and physical reactions (e. g., distillations) are facilitated by stirring/mixing the materials within a vessel. One way to do this is to stir the materials in a vessel with a mechanical stirrer. For example, a motor-driven rotatable spindle may be used in which one or more stirring members (e.g., blades) of the spindle can be positioned in the vessel to stir the materials.
As another example, a motor-driven magnetic stirrer may be used. In this stirrer, a magnetic stir bar is positioned within the vessel and a base magnet magnetically coupled to the stir bar is positioned under the vessel near the stir bar. A motor is used to rotate the base magnet, which in turn rotates the stir bar in the vessel to stir the materials. A magnetic stirrer is often desirable because minimal stirring structure is introduced into the vessel, reducing concerns of contamination or leakage to/from the vessel. In addition, small stir bars can be used which are easier to insert into vessels having small inlet openings such as round-bottom flasks (small inlet openings help prevent release of undesirable materials into the environment or vice versa).
However, strong base magnets are required with these magnetic stirrers, particularly when driving the stir bars in viscous materials or large volumes of materials (e.g., 20, 50 or 70 liters of materials). Traditional base magnets are often not strong enough to handle these conditions. In many cases, the coupling force between a traditional base magnet and the stir bar fails, resulting in the stir bar decoupling from the base magnet.
In addition, it is often desirable to conduct chemical reactions and/or physical reactions (e.g., distillations) under abnormal conditions, for example, under high vacuums or with highly volatile chemicals. These conditions can be adversely impacted by the components/design of the stirrer. For example, stirrer designs that have multiple joints or must be sealed would not function well in high vacuums. Similarly, electric motors would not be desirable where highly volatile chemicals are being used (e.g., where flammable or explosive materials are used).
Accordingly, it would be desirable to provide a motor-driven magnetic stirrer that can be used in high vacuum systems with highly volatile chemicals and that has a base magnet strong enough to handle highly viscous and large volumes of materials.
Corresponding reference characters represent corresponding parts throughout the views of the drawings.